IP-MPTCP(8) Linux IP-MPTCP(8)

ip-mptcp - MPTCP path manager configuration


ip [ OPTIONS ] mptcp { endpoint | limits | help }

ip mptcp endpoint add IFADDR [ port PORT ] [ dev IFNAME ] [ id ID ] [ FLAG-LIST ]

ip mptcp endpoint delete id ID [ IFADDR ]

ip mptcp endpoint change [ id ID ] [ IFADDR ] [ port PORT ] CHANGE-OPT

ip mptcp endpoint show [ id ID ]

ip mptcp endpoint flush

FLAG-LIST := [ FLAG-LIST ] FLAG

FLAG := [ signal | subflow | backup | fullmesh ]

CHANGE-OPT := [ backup | nobackup | fullmesh | nofullmesh ]

ip mptcp limits set [ subflow SUBFLOW_NR ] [ add_addr_accepted ADD_ADDR_ACCEPTED_NR ]

ip mptcp limits show

ip mptcp monitor

MPTCP is a transport protocol built on top of TCP that allows TCP connections to use multiple paths to maximize resource usage and increase redundancy. The ip-mptcp sub-commands allow configuring several aspects of the MPTCP path manager, which is in charge of subflows creation:

The endpoint object specifies the IP addresses that will be used and/or announced for additional subflows:

ip mptcp endpoint add add new MPTCP endpoint
ip mptcp endpoint delete delete existing MPTCP endpoint
ip mptcp endpoint show get existing MPTCP endpoint
ip mptcp endpoint flush flush all existing MPTCP endpoints

An IPv4 or IPv6 address. When used with the delete id operation, an IFADDR is only included when the ID is 0.

When a port number is specified, incoming MPTCP subflows for already established MPTCP sockets will be accepted on the specified port, regardless the original listener port accepting the first MPTCP subflow and/or this peer being actually on the client side. This option has to be used in combination with the signal flag.

is the network interface name attached to the endpoint. It is important to specify this device name linked to the address to make sure the system knows how to route packets from the specified IP address to the correct network interface. Without this, it might be required to add IP rules and routes to have the expected behavior.

is a unique numeric identifier, between 0 and 255, for the given endpoint. It is not possible to add endpoints with ID 0, because this special ID is reserved for the initial subflow. For rules linked to the initial subflow, the path-manager will look at endpoints matching the same address, and port if set, ignoring the ID.

The endpoint will be announced/signaled to each peer via an MPTCP ADD_ADDR sub-option. Typically, a server would be responsible for this. Upon reception of an ADD_ADDR sub-option, the other peer, typically the client side, can try to create additional subflows, see ADD_ADDR_ACCEPTED_NR.

If additional subflow creation is allowed by the MPTCP limits, the MPTCP path manager will try to create an additional subflow using this endpoint as the source address after the MPTCP connection is established. A client would typically do this.

If this is a subflow endpoint, the subflows created using this endpoint will have the backup flag set during the connection process. This flag instructs the remote peer to only send data on a given subflow when all non-backup subflows are unavailable. When using the default packet scheduler with a 'backup' endpoint, outgoing data from the local peer is also affected: packets will only be sent from this endpoint when all non-backup subflows are unavailable.

If this is a subflow endpoint and additional subflow creation is allowed by the MPTCP limits, the MPTCP path manager will try to create an additional subflow for each known peer address, using this endpoint as the source address. This will occur after the MPTCP connection is established. If the peer did not announce any additional addresses using the MPTCP ADD_ADDR sub-option, this will behave the same as a plain subflow endpoint. When the peer does announce addresses, each received ADD_ADDR sub-option will trigger creation of an additional subflow to generate a full mesh topology. This fullmesh flag should always be used in combination with the subflow one to be useful, except for the address used by the initial subflow, where subflow is then optional.

In some scenarios, an MPTCP subflow can use a local address mapped by a implicit endpoint created by the in-kernel path manager. Once set, the implicit flag cannot be removed, but other flags can be added to the endpoint. Implicit endpoints cannot be created from user-space.

The limits object specifies the constraints for subflow creations:

ip mptcp limits show get current MPTCP subflow creation limits
ip mptcp limits set change the MPTCP subflow creation limits

specifies the maximum number of additional subflows allowed for each MPTCP connection. Additional subflows can be created due to: incoming accepted ADD_ADDR sub-option, local subflow endpoints, additional subflows started by the peer.

specifies the maximum number of incoming ADD_ADDR sub-options accepted for each MPTCP connection. After receiving the specified number of ADD_ADDR sub-options, any other incoming one will be ignored for the MPTCP connection lifetime. When an ADD_ADDR sub-option is accepted and there are no local fullmesh endpoints, the MPTCP path manager will try to create a new subflow using the address in the ADD_ADDR sub-option as the destination address and a source address determined using local routing resolution When fullmesh endpoints are available, the MPTCP path manager will try to create new subflows using each fullmesh endpoint as a source address and the peer's ADD_ADDR address as the destination. In both cases the SUBFLOW_NR limit is enforced.

monitor displays creation and deletion of MPTCP connections as well as addition or removal of remote addresses and subflows.

Original Manpage by Paolo Abeni <pabeni@redhat.com>

4 Apr 2020 iproute2